Method of polishing diamonds.



G. A. DE GRAAF. METHOD OF POLISHING DIAMONDSf APPLICATION man JULY 10. I912- 2 SHEETSSHEET lwmvsssm v mun/Ton mm 4. de 004 ITTORIIEKS Patnted Jan. 23,1917.

" sas "EFFEQ? rm'rnon or romsnme DIAMQNDS.

To all whom it mag concern:

Be it known that I, GnRRrr A. on GRAAF, a subject of the Queen. of Holland, andresiding at Bloomfield, county of Essex, and

State of New Jersey, have invented certain new and useful Improvements in Methods of Polishing Diamonds, of which the following is a specification.

My invention. relates to an improved method of polishing diamonds whereby I- am enabled to polish diamonds across the grain which heretofore has been impossible by ordinary methods' The machine herein described is the joint invention of Benjamin de Graaf and myself, being shown in our application, Serial No. 606,115, filed February 2, 1911, and'is herein fully described because-l find it is adapted to be run at the high speeds required'to perform the operation of polishing diamonds by my improved method.

In the method heretofore employed in polishing diamondsthe speed of rotation of wheel has been maintained at 1800 to 2000 revolutions per minute, the

the polishing best results being obtained at about 1800 v revolutions. In machines asordinarily constructed the spindle of the lapidary wheel is provided with conical ends which blocks of hard wood such as pockwood. Such machines cannot safely be run at a speed much greater than 2000 revolutions per minute.

Experience has shown that when a wheel is run at speeds much above 1800 revolutions the polishing of diamonds becomes impractical owing to vibrations of the wheel;

this tremor of the wheel increasing with-the.

speed until it becomes impossible to polish diamonds with any degree of satisfaction.

The speed at which this tremor of the wheel takes place varies with the weight and di ameter of the wheel, but I have found that usually the wheel ordinarily used passes the tremor stage and begins to quiet down and get steady again as the speed approximates 3000 revolutions per minute.- Hence,

. on account'of 'the tremor of the wheel at 0 speeds much above 1800,'it has become a fixed rule among diamond polishers that the best results are to be obtained when the wheel is run at approximately .1800 revolutions per minute and higher speeds cannot be used satisfactorily; and as previously stated extremely higher speeds cannot be Specification of Letters Patent.

are set into conical pockets or bearings in safely obtained on the ordinary machine 1 have demonstrated the above tremor action of the wheel by running the machine at various speeds but 1 have found that after passing, the tremor or non-polishing stage and carrying the speed of the wheel beyond this period the wheel will again begin to be effective; and diamonds can be polished even more rapidly than has heretofore been possible. These peculiar phenomena seem to proceed about as follows: at a speed of 1800 to 2000 the diamonds will be polished as usual; increasing the speed to slightly more than'2000' it is found that the effectiveness has decreased; further increase in the speed Patented Jan. as, rare. Application filed July 10, 1912. Serial H0. 708,560.

7c) of the wheel for polishingthe diamonds of the wheel 'still further diminishes the polishing. efiect of the wheel. After passing the period of tremor or as the speed approaches 3000revolutions the wheel again begin totake holdand polish -dia monds satisfactorily.

With the ordinary machines, much above 2000 revolutions are dangerous, for the bearings are likely to give way and permit the wheel to sible to run the wheel at any speed desired up to from 7000 to 10,000 revolutions per minute. I have obtained very satisfactory results at a speed of 7500.

Another important feature of my improved method is that I can polish diamonds which it has been impossible to polishby the speeds of. 8

fly out. .With the ma-j chine herein described, however, it is posusual method and speed of the ordinary ma-I v chine. Many diamonds, in the rough, are.

so shaped that to cut and polish themaccording to the cleavage the diamond will be lost than it is worth to full value of such diamonds attempts have been made to polish them across the grain, but with the speed of practically more of 5 '9 polish the small remaining part'. To get the quired. Many otherwise valuable stones. are,

for this reason, lostas gems and must be sold at much lower rates to be used in the arts for drills, glass cutters or the like or as diamond chips and powder.

Now, by

above described, and at high wheel speeds grain as fast or faster than diamonds are my method of polishing diaemonds at speeds beyond the tremor period,

-...1 0 I am enabled to polish diamonds across the method and speed.

polished in the ordinary way by the usual This is important for, since by the ordinary method, it is impossible or prohibitively expensive to polish diamonds across the grain, diamond experts must be employed to split, cut and prepare the diamonds for the predetermine the locationof the facets so that, if possible, no polishing across the grain will be required. It is readily understood that by my method this expensive supervision and direction on the part of an expert is not required for. it makes no difference whether the facets are cut across the grain or not, hence'unskilled labor can do all the work. I am thus enabled 'to save to the gem trade large numbers of diamonds and to reduce the cost of polishing diamonds, for with my method sary to cut and polish the diamonds accordi g to cleavage but they can be polished in any way which will give the best results and produce the largest finished diamond. A test of my method was made as follows: diamond to be polished across the grain was fitted in a dop and the attempt was made to polish it by the ordinary method under the best possible conditions obtainable on a regular machine. After keeping the diamond in contact with the wheel for aconslderable period no appreciable progress was made and the effort was finally abandoned. Without changing or removing the diamond from the dop it was secured in place in my machine, and at a speed of approximately 7500 revolutions per minute a perfect facet was cut (across the grain) in 14 minutes..-

By my high speed method I accomplish something heretofore impossible and save to the gem trade many diamonds otherwise discarded because they couldnot be cut across the grain while, at" the same time, reducing the time and expense of polishing diamonds.

The improved diamond polishingmachine illustrated in the accompanying drawin is adapted to be run at the high speeds required to carry out my new method of polishing diamonds.

Figure 1 is a side elevation of the machine partially in sectidn. Fig. 2 represents a plan view of the lower bearing box, Fig. .3 represents the upper bearing 1 in section, Fig. 4 is a vertical section ofthe lower bearing, Fig. 5 is a vertical section of the upper bearing and Fig. 6 is a view of the clamping plate for the upper bearing.

Any suitable support may be provided for carrymg the polis g wheel and accessories required, but in .th have illustrated a machine in resent the frame carrying tending shelf or bracket 2' to support the lower bear-in a forwardlyi exwhich is adapted -box. Abracket 3 extending forwardly and upwardly is polishing wheel and it is not necesor diamond holding may be employed.

bearing box 16 "is secured to suitable bolts 17 arranged in any desiredthrough holes 18 in in Fig. 2 of the drawings. The box 16 is ppening threaded 22 between the which I rep upper end of the sp adapted to support the upper bearing block. Mounted uponthe main frame 1 of the machine is a second bracket 4 which is adapted to support two idler pulleys 5 over which the belt 6 passes in order to change its di rection in the well known manner. A main driving pulley 7, around which the belt 6 passes, is mounted on the main shaft 8 which latter may be driven in any suitable manner, the belt 6 after passing over the idler pulleys 5 passes around a pulley 9 secured to the shaft or spindle 10 which is adapted to rotate in suitable bearings, and carries the polishing wheel 11 secured thereto in any suitable and preferred manner. The wheel 11 is'So located on the spindle 10 that it r0- tates just above the shelf or table top 12 upon which the stand or bracket 13. rests. his bracket 13 has an. outwardly extending clamping arm 14 which is adapted to clam and hold in place the dop or ing chuck 15. Any suitable diamond hol 4 form of dop device may be used'and of holding the same in to the polishing wheel any suitable method operative relation 1n, order to obtain the'high speeds required for polishing diamonds by my method it is necessary to provide bearings for the spindle of the wheel which shall be absolutely safe and reliable when the wheel is runat extremely high speed. For this purpose the machine is provided with a lower of special construction which the bracket projection 2 by manner, as, for instance, by passing them the lugs 19', illustrated hollow and partially closed at the top, the top portion being at 20 to receive a thimble or bearing box 21 provided with a correspondingly threaded portion near the top thereof to cooperate with the threads 20 in gs the top of the box 16. -The bearing box 21 extends downward'into'the interior of the box16 thereby box 16 andthe lower end of the bearing box 21. This closed annular chamber is adapted for use as a grease or provided with a circular A forming anannular chamber oil cup for lubricating the lower bearing of the spindle 10. orthis purpose the bearing box 21 is provided with a plurality of perforations 23 about its'cylindrical surface and one through the center of the lower end, the latter perforation or hole being adapted to serve as a thrust bearing forthe lower conical end 24 well as to provide lub indle 10 extends intoa bearing box 25 which issupported by the upwardly and forwardly extending bracket 3 and is adapted to be removably clamped into place bymeans of a plate 26 (illustrated lcation therefor. The

of the spindle 10, as

ed hole 29 through of the bearing block be screwed, and

410 parts.

45 it is desired to remove any purpose,

' the polishing in Fig. 6) which is bolted to the upper end of the bracket 3. One bolt hole 2 in this clamping platecis cut away to form an open slot sov that the plate may be swungaround 5 one of the bolts 28 as a center and carry it I ner end, thereb adapting it to be readily turned so as to rmly clamp the bearing box 15 in the upper endof the bracket 3, as ind cated in Figs. 3 and 5 of thedrawings. Thls upper bearing block 25 is adapted to provide cylindrical-and thrust upper end of the spindle 10. The upper end 25 is internally threaded at 31, into which a threaded plug 32 may then clamped or held in place after proper adjustment by a lock nut 33. The plug 32 and the lock nut 33 are 25 each provided with wings so that they may be properly adjusted and clamped. The end plug 32 is rovided with a central hole which at itsowe'r end is adapted to receive the upper conicala'oand to serve as a thrustbearing therefor.

point 3% of the spindle 10 The upper end-10f the plug is V prov1ded with an internally threaded'socket35 into which anoil cup. 36 'may 'be' screwed as indicated in Fig." 1 ofthe drawings By. means of the central openingfi'l in the plug 32,

communication" is between the oil cup and the conical and cylindrical end vidingfl the necessary lubrication for t ese 'For the construction described for the upperbearing block and bracket support, it will'readily be understood that the bearing box25 may be unclamped and remoived when the spindle 10 for as for instance, for turning oft wheel 11 or for replacing the sameby a new wheel when such changes are required. This arrangement of cylindrical bearings for the.

0 of the -sp1ndle' =10 1n the bearing box 25.'thereby roand conical thrust bearing forfeach end of the spindle 10 particularly adapts the ma- .chine for high speed. operation as required. in carrying out my improved method of polishing diamonds. I have operated a machine of this construction at approximately 7 500 iievolutions per minute with perfect safety and have thereby'been enabled to polish diamonds across the grain, which, heretofore has been impossible or impracticable, as well as with the grain, much more rapidly than has heretofore been accomplished. Itwill be understood that various modifications may be made in the machine or its operation without departing from the spirit and scope of my invention as set forth in the appended claims.

1 I claim:

1. The process of polishing diamonds which consists in suitably coating the surface of a lapidary wheel adapted for polis'hing diamonds, speeding it past the stage.

of initial wabbling and thenup to approximately' 1900 revolutions per minute at which speed the wheel runs true and is capable of cutting diamonds in the ordinary manner,

while bringing a diamond into contact with the surface of said whee 2. An improvement in the art of polishing diamonds which consists in preparing an abrasive surface of oil and diamond dust and moving the same at high velocity across increasing the the grain of ardiamond to produce a facet thereon, said abrasive being movedat a ve- ;locity of not less than 7000 feet per minute.

In witness whereof I have hereunto set my hand in the presence of'two subscribing witnesses.

GERRIT A. m: GBAAF. Witnesses: I MAY 0. VANDERHOOF,

FRANCES B. STEWART. 

